Pseudoporous surface of implantable materials and methods of making the same

Abstract

An implantable medical device can include an electrode substrate electrically connected to at least one electrode. The device can have a pseudoporous surface across the electrode substrate and electrode. This surface can result in a real surface area (RSA) greater than the geometric surface area (GSA) of the device. The pseudoporous surface can be a macroporous surface enabling a charge injection capacity greater than 1 mC/cm 2 while minimizing rejection of the device by surrounding tissue in chronic implant applications. The electrode can be a thin layer of conductive material, such as platinum or another metal, conformally deposited on the pseudoporous surface of the electrode substrate. A method of making the implantable device can include forming the device having an electrode substrate and at least one electrode electrically coupled to the electrode substrate, and forming a pseudoporous surface on the electrode substrate and electrode.

What is claimed is: 
     
       1. An implantable medical device comprising:
 a) an electrode substrate having a pseudoporous surface; 
 b) at least one electrode electrically connected to the electrode substrate, wherein the electrode is a layer of electrically conductive material conforming to the pseudoporous surface of the electrode substrate such that the electrode also has the pseudoporous surface. 
 
     
     
       2. The device of  claim 1 , wherein a real surface area (RSA) of the pseudoporous surface is greater than a geometric surface area (GSA) of the pseudoporous surface. 
     
     
       3. The device of  claim 2 , wherein the RSA is from 2 to 100 times greater than the GSA. 
     
     
       4. The device of  claim 1 , wherein a roughness of the pseudoporous surface is root mean square (RMS) of height measurements, wherein the RMS is from 10 to 60 nanometers. 
     
     
       5. The device of  claim 1 , wherein the pseudoporous surface has pore depths from about 1 μm to about 10 μm. 
     
     
       6. The device of  claim 1 , wherein the pseudoporous surface has an average pore width from about 500 nm to about 5 μm. 
     
     
       7. The device of  claim 1 , wherein the pseudoporous surface is a macro-porous surface having a charge injection capacity greater than 1 mC/cm 2 . 
     
     
       8. The device of  claim 1 , wherein the pseudoporous surface is a macro-porous surface having a charge injection capacity greater than 10 mC/cm 2 . 
     
     
       9. The device of  claim 1 , wherein the pseudoporous surface is a macro-porous surface having a charge injection capacity greater than 20 mC/cm 2 . 
     
     
       10. The device of  claim 1 , wherein the layer of electrically conductive material has a thickness from about 50 nm to about 1 μm. 
     
     
       11. The device of  claim 1 , wherein the at least one electrode is formed of platinum. 
     
     
       12. The device of  claim 1 , wherein the at least one electrode includes an exposed electrical contact and remaining portions of the implantable device are coated with an electrically insulative material. 
     
     
       13. The device of  claim 1 , wherein the pseudoporous surface covers substantially all surfaces of the electrode substrate and the at least one electrode. 
     
     
       14. The device of  claim 1 , wherein the pseudoporous surface covers at least 50% of surfaces of the electrode substrate and the at least one electrode. 
     
     
       15. The device of  claim 1 , wherein the implantable device is selected from the group consisting of a Utah electrode array, a cochlear implant, an EKG electrode, and a pacemaker. 
     
     
       16. The device of  claim 1 , wherein the implantable device is a Utah electrode array. 
     
     
       17. The device of  claim 1 , wherein the pseudoporous surface is formed by etching the electrode substrate, then conformally depositing the electrode on the etched electrode substrate. 
     
     
       18. The device of  claim 1 , wherein the electrode substrate comprises silicon. 
     
     
       19. The device of  claim 1 , wherein the device is shaped as a needle.